Comparison of methods to determine the degree of gelatinisation for both high and low starch concentrations

A general procedure was developed to measure the degree of gelatinisation in samples over a broad concentration range. Measurements based on birefringence, DSC (Differential scanning calorimetry), X-ray and amylose–iodine complex formation were used. If a 10 w/w % wheat starch–water mixture was used, each method resulted in approximately the same degree of gelatinisation vs. temperature curve. In case the gelatinisation of a 60 w/w % wheat starch–water mixture was followed as a function of the temperature, each method resulted in a different degree of gelatinisation vs. temperature curve. DSC and X-ray measurements are preferred, because they can be used to determine when the final stage of the gelatinisation process has been completed. Birefringence and amylose–iodine complex formation measurements are suitable alternatives if DSC and X-ray equipment is not available, but will lead to different results. The differences between the methods can be explained by considering the phenomena that take place during the gelatinisation at limiting water conditions.

Based on the experimental data obtained with DSC and X-ray measurements, the gelatinisation of 10 w/w % and 60 w/w % wheat starch–water mixtures started at the same temperature (approximately 50 °C). However, complete gelatinisation was reached at different temperatures (approximately 75 °C and 115 °C for, respectively, 10 w/w % and 60 w/w % wheat starch–water mixtures) according to the experimental DSC and X-ray data. These results are in accordance with independent DSC measurements that were carried out.

The Flory equation was adapted to provide a quantitative explanation for the curves describing the degree of starch gelatinisation as a function of the starch–water ratio and the temperature. The gelatinisation curves that were obtained with the model are in good agreement with the experimentally determined curves. The parameters , ΔH_u and χ₁₂ that resulted in the lowest sum of the squared residuals are 291 ± 63 °C, 29.2 ± 3.9 kJ/mol and 0.53 ± 0.05 (95% confidence interval). These values agree with other values reported in literature.     

牛血清白蛋白在聚乙二醇/葡聚糖双水相体系中分配特性的研究

采用考马斯亮蓝G250染色法测得室温下BSA在PEG/dextran双水相体系中的分配系数。以BSA在PEG/dextran体系的下相富集为目标,研究了PEG的分子量、浓度、dextran浓度以及所加入中性盐的种类与浓度、体系pH诸因素对其分配特性的影响。实验结果表明,在PEG4000/dextran体系中,采用PEG质量分数9%-dextran质量分数9%的浓度组成,同时在pH=7.0,NaC l浓度为0.2 mol.L-1或pH6.0,NaC l浓度为0.34 mol.L-1的工艺条件下萃取BSA均可达最小分配系数,其值为0.014。     

Effect of Salmonella minnesota R595 LPS on the dipalmitoylphosphatidyl-ethanolamine (DPPE)-dipalmitoylglycerol (DPG)-water model membrane system

The effect of Salmonella minnesota R595 lipopolysaccharide (LPS) on model membrane consisting of a mixture of fully hydrated lipids (dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylglycerol (DPG)) was investigated by differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and freeze–fracture methods. The DPPE–DPG/water system forms a multilamellar arrangement in the gel phase which transforms into a mixture of inverted hexagonal and cubic structures. By the presence of LPS the thermotropic behaviour of the system was affected significantly only at its high concentration (1:1 mol/mol LPS/DPPE–DPG) in the gel phase, while above the chain melting transition the ratio of the inverted cubic and the hexagonal structures was changed and at the 1:1 mol/mol LPS/DPPE–DPG ratio a complex and amorphous phase was formed. The structural parameters of the inverted hexagonal and cubic phases are modified by the temperature and also by the LPS concentration, as deduced from the characteristic SAXS curves. Summarizing the effects of the LPS molecules on the DPPE–DPG/water vesicle system a schematic phase diagram was constructed.     

Chitin fractionation and characterization in N,N-dimethylacetamide/lithium chloride solvent system

A detailed study of the interaction of chitin molecular species with the solvent system N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl) allowed the development of a new method for chitin fractionation by coacervate extraction. The controlled increase of the extracting power of the solvent was carried out using slight modification of the solvent composition. Partial extractions of molecular species were done between coacervation and complete dissolution limits using different mixtures of DMAc/LiCl of increasing extracting power. Fractions were characterized in DMAc/LiCl 5% (w/w) by viscometry and size exclusion chromatography with refractive index and multi-angle laser light scattering detectors. Fractions obtained by coacervate extraction range from 80,000 to 710,000 g mol⁻¹ with polydispersity index between 1.28 and 1.44. The Mark–Houwink–Sakurada equation constants a and K for chitin in DMAc/LiCl 5% (w/w) were found to be 0.95 and 7.6×10⁻⁵ dl g⁻¹, respectively.     

A new device for measurement of the thermal conductivity of fur and blubber

1. 1. A new and simple device for measurements of thermal conductivity of fur and blubber is described.

2. 2. The device measures temperature differences across the sample and across a polyethylene plate with known conductivity which is placed in series with the sample.

3. 3. The conductivity of the polyethylene was determined from the steady state temperature difference and heat flux through the wall of a polyethylene pipe with a central heat source.

4. 4. The accuracy of the device is ±4.0%.

5. 5. The thermal conductivity of harp seal (Phoca groenlandica) and minke whale (Balaenoptera acutorostrata) blubber, as determined by use of this device, is very close to previously reported values.

Sydonol,a New Fungal Morphogenic Substance Produced by an Unidentified Aspergillus sp.

The “intrinsic” thermal conductivity values of unfrozen wet egg-albumin, wheat gluten and milk casein were determined on the basis of the series heat conduction model to be 0.238, 0.219 and 0.200 [W/m·°C], respectively. The corresponding values for frozen samples were 0.403, 0.315 and 0.273 [W/m·°C], respectively. The “intrinsic” thermal conductivity values of wet proteins determined in the previous and present studies were between the thermal conductivity values of water (or ice) and oils (or fats), in the reverse order of the average hydrophobicity values of proteins.     

Thermoregulatory effects of central injection of noradrenaline in the new-born columbian ground squirrel (Spermophilus columbianus)

1. 1.Effects of centrally injected noradrenaline (NA) into new-born (12–300 h. post-partum) Columbian ground squirrels (Spermophilus columbianus) were studied to provide comparative data on ontogeny of the thermoregulatory pathways in a hibernating species.

2. 2.At warm ambient temperatures (32–34°C, similar to nest temperature), NA increased heat production (47–92%). rectal temperature (0.27–1.73°C), and axillary temperature (0.59–1.92°C). Peak magnitudes of heat production increased with increasing age on a per unit weight basis.

3. 3.At lower temperatures (28–31°C), NA had no effect on heat production.

4. 4.The data indicate that metabolic and thermal responses to NA in neonates of hibernating species are comparable (e.g. rabbit. guinea pig) or different (e.g. lamb) from those observed in neonates of non-hibernating species.

Study of the interaction of artemisinin with bovine serum albumin

The study on the interaction of artemisinin with bovine serum albumin (BSA) has been undertaken at three temperatures, 289, 296 and 303 K and investigated the effect of common ions and UV C (253.7 nm) irradiation on the binding of artemisinin with BSA. The binding mode, the binding constant and the protein structure changes in the presence of artemisinin in aqueous solution at pH 7.40 have been evaluated using fluorescence, UV–vis and Fourier transform infrared (FT-IR) spectroscopy. The quenching constant K_q, K_sv and the association constant K were calculated according to Stern–Volmer equation based on the quenching of the fluorescence of BSA. The thermodynamic parameters, the enthalpy (ΔH) and the entropy change (ΔS) were estimated to be −3.625 kJ mol⁻¹ and 107.419 J mol⁻¹ K⁻¹ using the van’t Hoff equation. The displacement experiment shows that artemisinin can bind to the subdomain IIA. The distance between the tryptophan residues in BSA and artemisinin bound to site I was estimated to be 2.22 nm using Föster's equation on the basis of fluorescence energy transfer. The decreased binding constant in the presence of enough common ions and UV C exposure, indicates that common ions and UV C irradiation have effect on artemisinin binding to BSA.     

Binding of anti-inflammatory drug cromolyn sodium to bovine serum albumin

Fluorescence spectroscopy in combination with circular dichroism (CD) and UV–vis absorption spectroscopy were employed to investigate the binding of anti-inflammatory drug cromolyn sodium (Intal) to bovine serum albumin (BSA) under the physiological conditions with Intal concentrations of 0–6.4 × 10⁻⁵ mol L⁻¹. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by Intal is a result of the formation of Intal–BSA complex. Quenching constants were determined using the Stern–Volmer equation to provide a measure of the binding affinity between Intal and BSA. The thermodynamic parameters ΔG, ΔH, ΔS at different temperatures (298, 304, and 310 K) were calculated and the results indicate the electrostatic interactions play a major role in Intal–BSA association. Binding studies concerning the number of binding sites (n = 1) and apparent binding constant K_b were performed by fluorescence quenching method. Utilizing fluorescence resonant energy transfer (FRET) the distance R between the donor (BSA) and acceptor (Intal) has been obtained. Furthermore, CD and synchronous fluorescence spectrum were used to investigate the structural change of BSA molecules with addition of Intal, the results indicate that the secondary structure of BSA molecules was changed in the presence of Intal.     

Modeling of the primary and secondary drying stages of the freeze drying of pharmaceutical products in vials: numerical results obtained from the solution of a dynamic and spatially multi-dimensional lyophilization model for different operational policies

A rigorous unsteady state and spatially multidimensional model is presented and solved to describe the dynamic behavior of the primary and secondary drying stages of the lyophilization of a pharmaceutical product in vials for different operational policies. The results in this work strongly motivate the aggressive control of freeze drying and it is found that heat input control that runs the process close to the melting and scorch temperature constraints yields (i) faster drying times, and (ii) more uniform distributions of temperature and concentration of bound water at the end of the secondary drying stage.     

Measurement of the Thermal Conductivity of Unfrozen and Frozen Food Materials by a Steady State Method with Coaxial Dual-cylinder Apparatus

Coaxial dual-cylinder apparatus was used to measure the effective thermal conductivity of aqueous solutions of glucose, sucrose, gelatin and egg albumin over a temperature range from –20° to 20°C by the steady state method. The accuracy of the apparatus was confirmed by testing with water and ice. The effective thermal conductivity decreased with an increase in the total solid content in both the frozen and unfrozen states. In the unfrozen state, the effective thermal conductivity was slightly dependent on temperature. In the frozen state, however, the effective thermal conductivity was strongly dependent on temperature; lower temperatures gave higher effective thermal conductivity, reflecting the increase in the ice fration. For the unfrozen samples, the intrinsic thermal conductivity of each solid component was calculated by heat transfer models. All the models tested, series, parallel and Maxwell–Eucken, were equally applicable to describe the heat conduction in the unfrozen state. In the frozen state, however, the strong temperature dependency of the effective thermal conductivity suggests that the effect of the temperature dependency of the ice fraction should be incorporated into theoretical models.     

The Effect of Sugars and Polyols on the Heat Resistance of Salmonellae

S ummary . The heat resistance at 65° of 3 strains of salmonellae in solutions of sugars or polyols was enhanced as the concentration of the solutes increased. There was no linear relationship between heat resistance and water activity ( a_w ), but for all solutes except glycerol there was a linear relationship between log D ₆₅ and concentration (% w/w) of solute. Comparison of D ₆₅ at a particular a_w or percentage (w/w) solute concentration showed that the value decreased in the order: sucrose > glucose > sorbitol > fructose > glycerol. In glycerol, D ₆₅ values were always very much lower than in any other solute. With sucrose–glycerol or sucrose–glucose mixtures, heat resistance depended both on the total concentration (% w/w) of solutes present and also on the a_w of the solution.     

Bovine serum albumin partitioning in an aqueous two-phase system: Effect of pH and sodium chloride concentration

The partitioning of bovine serum albumin (BSA) in a polyethylene glycol 3350 (8% w/w)–dextran 37 500 (6% w/w)–0.05 M phosphate aqueous two-phase was investigated at different pHs, at varying concentrations of sodium chloride at 20°C. The effect of NaCl concentration on the partition coefficient of BSA was studied for the PEG–dx systems with initial pH values of 4.2, 5.0, 7.0, 9.0, and 9.8. The NaCl concentrations in the phase systems with constant pH value were 0.06, 0.1, 0.2, 0.3, and 0.34 M. It was observed that the BSA partition coefficient decreased at concentrations smaller than 0.2 M NaCl and increased at concentrations greater than 0.2 M NaCl for all systems with initial pHs of 4.2, 5.0, 7.0, 9.0, and 9.8. It was also seen that the partition coefficient of BSA decreased as the pH of the aqueous two-phase systems increased at any NaCl salt concentration studied.     

Effect of inoculum preparation and formulation on survival and biocontrol efficacy of Pseudomonas fluorescens F113

Sugarbeet seeds used by farmers are often pelleted using an EB^TM-based mix. During the pelleting process, the seeds are dried immediately after application of the mix. In this work, the effects of inoculum preparation and formulation on survival and biocontrol efficacy of Pseudomonas fluorescens F113Rif were investigated using a 1:1 EB^TM/vermiculite mix and sugarbeet seeds pelleted with this material. Growing F113Rif for 3 d (28 °C) within the EB^TM/vermiculite mix amended with nutrients (sucrose asparagine broth), instead of adding the cells to the unamended mix immediately before drying the mix or the pelleted sugarbeet seeds, resulted in improved survival of the strain in the mix or on the seeds, respectively, during subsequent storage. A slower drying (20 h instead of 3 h) of the F113Rif-inoculated EB^TM/vermiculite mix to 11% w/w water content enhanced strain survival in the mix during storage, but the drying conditions studied had no effect on inoculant survival on the seed during storage when pelleted seeds were dried to 10% w/w water content. Biological control of damping-off disease of sugarbeet (caused by Pythium spp.) in soil microcosms was achieved when F113Rif was inoculated in the unamended mix 3 d before pelleting the seeds, but not when nutrient-amended mix was used. Inoculum preparation and drying of the formulation are key factors to consider when optimizing the use of a commercial EB^TM/vermiculite seed formulation for delivery of a biocontrol Pseudomonas inoculant.     

Analysis and Prediction of the Effective Thermal Conductivities of Meats

Published data of the effective thermal conductivities of meats were analyzed in relation to approximate compositions of the meats. On the basis of series heat conduction model, the “intrinsic” thermal conductivity value of meat protein was estimated to be 0.342 [W/m · °C] when unfrozen, and 0.581 [W/m · °C] when frozen. Using these “intrinsic” values and the series heat conduction model, the effective thermal conductivities of meats were reversely predicted from the contents of water and fat. Standard deviations of the published data from the predictions were ± 7.0% for unfrozen meats and ± 15.4% for frozen meats. If heat flow is parallel to the meat grain, published data for frozen meats are higher than the predictions by about 20% as a mean.     

Determination of aqueous two-phase system phase-forming components in the presence of bovine serum albumin

In the current work, the quantification of different poly(ethylene glycol) (PEG)–potassium phosphate/sodium citrate aqueous two-phase system (ATPS) phase-forming components was investigated by using conductivity and refractive index measurements. For this purpose, refractive index and conductivity calibration curves were obtained for ATPS at different pH values in the presence of different bovine serum albumin (BSA) concentrations. Whereas BSA had no effect on the conductivity, it had a considerable effect on the refractive index. Finally, a convenient dilution of the samples prior to the ATPS constituent determination is needed to ensure no significant influence from BSA.     

Phase behavior of the monoerucin/water system

Monoerucin is a monoacylglycerol incorporating a cis monounsaturated fatty acid, 22 carbon atoms long, with the double bond at carbon number 13. The original temperature-composition phase diagram for the monoerucin/water system, constructed on the basis of ‘consistency’ and light microscopy, includes unexpectedly only the lamellar and fluid isotropic phases [Lutton, E.S., 1965. J. Am. Oil Chem. Soc. 42:1068–1070]. In separate studies using X-ray diffraction, the cubic phase [Larsson et al., 1978. J. Sci. Food Agric. 29:909–914] and the inverted hexagonal (H_II) phase [Caffrey, M., 1989. Biophys. J. 95:11–21] were shown to be the dominant phases. We have resorted to the traditional isoplethal diffraction method for constructing the equilibrium phase diagram of monoerucin in water with a view to resolving the controversy regarding the thermotropic and lyotropic properties of the system. The study confirms the presence of the pure H_II phase that extends from ca. 10 to 22% (w/w) water and from ca. 35 to 125°C, and its coexistence with excess water above ca. 24%(w/w) water in the same temperature range. The low temperature region of the diagram is dominated by the lamellar crystal (L_c) phase, with the existence of the lamellar liquid crystal (L) and cubic-Ia3d phases at intermediate temperatures and hydration levels. Differential scanning calorimetry and polarizing light microscopy were used to confirm the reported equilibrium phase behavior. Full structure characterization of the system and how phase microstructure depends on sample hydration and temperature are reported.     

Use of the twin-cell differential titration calorimeter for binding studies. I. EDTA and its calcium complex

The use of a twin-cell differential titration calorimeter is described which utilizes small volumes (1–3 ml) of modest concentrations of materials (0.001–0.01 M) and yield data of good precision. Operation is controlled by a microprocessor which regulates and controls the addition of reagents and collects and displays the data as time, temperature in volts, and the pH. Corrections for the titration of water are applied to the potentiometric data, and the thermal data are corrected for the initial temperature-time baseline, the changes in heat capacity, and the heat loss (or gain) to the external environment. Finally, the thermal signal is corrected for the heat derived from the formation of water due to the free hydrogen or hydroxyl ions present. The corrected data as pH, groups titrated adn ΔH_T (kcal/mol) can then be used to obtain the parameters pK′ and ΔH_i involved with the equilibria by curve-fitting the observed data.

The system has been applied to the ionization of EDTA and its calcium complex. The ionization constants, the heats of ionization, the stoichiometry of binding and the heat of binding have been determined and demonstrated to be in agreement with published values.     

Nutrient removal by thermophilic Fischerella (Mastigocladus laminosus) in a simulated algaculture process

A novel nutrient removal/waste heat utilization process was simulated using semicontinuous cultures of the thermophilic cyanobacterium Fischerella. Dissolved inorganic carbon (DIC)-enriched cultures, maintained with 10 mg l⁻¹ daily productivity, diurnally varying temperature (from 55°C to 26–28°C), a 12:12 light cycle (200 μE sec⁻¹ m⁻²) and 50% biomass recycling into heated effluent at the beginning of each light period, removed > 95% of NO₃⁻ + NO₂⁻−N, 71% of NH₃-N, 82% of PO₄³⁻ −P, and 70% of total P from effluent water samples containing approximately 400 μg l⁻¹ combined N and 60 μg l⁻¹ P. Nutrient removal was not severely impaired by an altered temperature gradient, doubled light intensity, or DIC limitation. Recycling 75% of the biomass at the end of each light period resulted in unimpaired NO₃⁻ + NO₂⁻ removal, 38–45% P removal and no net NH₃ removal. Diurnally varying P removal, averaging 50–60%, and nearly constant > 80% N removal, are therefore projected for a full-scale process with continuous biomass recycling.     

Differential scanning calorimetric studies on bovine serum albumin: II. Effects of neutral salts and urea

Using defatted and SH-blocked bovine serum albumin (BSA), measurements of differential scanning calorimetry (d.s.c.) have been made mainly in NaSCN solution. BSA undergoes a heat-induced conformational transition in a particular range of pH and ionic strength and is separated into two thermally independent units, each of which has different thermostability in acidic and alkaline pH regions. Comparisons were made of the pH dependencies of the enthalpy of thermal denaturation (ΔH) and the temperature of thermal denaturation (T_d) in 0.01 NaSCN with those in 0.01 NaCl. It has been found that the stabilizing effect of NaSCN on BSA is larger than that of NaCl at pH 3.5–8, and that the heat-induced transition occurs by the electrostatic repulsive forces among the positively charged amino acid residues in a segment Arg 184–Arg 216 containing Trp 212 and the primary binding sites of anions. At ionic strength 0.01, the relative effectiveness of anions in suppressing the heat-induced transition and increasing the thermostability of BSA follows the order ClO₄⁻ − SCN⁻ > I⁻ > SO₄²⁻ > Br⁻ > Cl⁻. At ionic strength 0.1, the heat-induced transition is suppressed in all the salt solutions, and a T_d increase follows the order ClO₄⁻ SCN⁻ > I⁻ > Br⁻ > Cl⁻ SO₄²⁻. Thus, the highly chaotropic ions thermostabilize BSA more markedly than kosmotropic ions in the low and moderate salt concentrations. In contrast, chaotropic ions destabilize BSA and kosmotropic ions stabilize BSA at the higher concentrations. An adequate amount of NaCl or NaSCN prevents the destruction of the environment of the binding site in the segment containing Trp 212 in 4 urea solution at pH 7.0.